The present invention relates to an oil feeding system for a scroll compressor and, more particularly, to an oil feeding system for the rotary shaft of a scroll compressor having an enclosed vessel accommodating a scroll compressor proper and an electric motor, the enclosed vessel maintaining a low-pressure atmosphere therein.
Japanese Utility Model Unexamined Publication No. 59-88290, particularly FIG. 3, thereof show a conventional oil feeding system for a scroll compressor having an enclosed vessel accommodating a scroll compressor proper and an electric motor, and an oil reservoir formed at the bottom of the vessel wherein, an electric motor section is disposed at an upper portion of the enclosed vessel while a scroll compressor section is disposed at a lower portion thereof. A suction chamber surrounding the electric motor section and a discharge chamber surrounding a stationary scroll are formed separately from each other, with the oil reservoir at the bottom of the enclosed vessel being formed in the discharge chamber, so that oil in the oil reservoir can be supplied to various sliding portions such as the rotary shaft by use of the differential pressure between the discharge pressure and the suction pressure.
With this arrangement, however, since the oil is exposed to a high temperature, its viscosity becomes so low that it forms oil films only with difficulty. In addition, bearings do not serve much to remove the generated heat. Further, under certain operating conditions in which the differential pressure between the suction pressure and the discharge pressure is small, it is difficult to ensure an adequate amount of oil supply.
Japanese Patent Unexamined Publication No. 62-87693 shows an arrangement in which a scroll compressor section is disposed at an upper position while an electric motor section is disposed at a lower position, with the interior of an enclosed vessel being maintained at a low-pressure atmosphere, and an oil reservoir at the bottom of the vessel being maintained in a low-pressure atmosphere. An oil feeding system comprises a centrifugal pump associated with an eccentric hole formed in a crankshaft, and a lubricating pump disposed between the end of the shaft of a gyratory scroll and the opposing portion of the bottom of an eccentric hole formed in a drive shaft, with the two pumps drawing oil from an oil reservoir to supply oil to various sliding portions.
With the oil feeding system according to the last mentioned Japanese Publication, however, problems such as the following are encountered. The head of oil being supplied is long, and, as stated before, two pumps, i.e. the centrifugal pump and the lubricating pump, are necessary. In addition, the lubricating pump suffers from a large passage loss in its suction and discharge passages as well as from pulsation of discharged oil because of the intermittently repeated sucking and discharging actions of the pump.